Morphological Change of Cerebral Aneurysm with Possible Pseudoaneurysm at A2/3 of the Anterior Cerebral Artery on Three-dimensional Computed Tomographic Angiography.

Intracranial pseudoaneurysm formation due to a ruptured nontraumatic aneurysm is rare. We describe a case of ruptured aneurysm, which showed morphological change on radiological examinations. An 83-year-old woman developed subarachnoid hemorrhage (SAH) with ventricular rupture and intracerebral hematoma in the corpus callosum. Contrast-enhanced computed tomography (CE-CT) demonstrated an aneurysm at the right A2/3 junction of the anterior cerebral artery. CE-CT repeated 17 h after the initial one showed shortening of the lesion on both three-dimensional and raw images. The aneurysm was surgically clipped. In cases of SAH with a hematoma or thick SAH, there is a possibility that a pseudoaneurysm will form at the tip of the true aneurysm in an adjacent thrombus or existence of intraluminal thrombus. The morphology may change during the period between initial radiological evaluation and the operation in these cases. We should be aware that the intraoperative findings or subsequent radiological findings might be different from those observed on preoperative radiological examinations.